Abstract: To study the dynamic propagation characteristics of mode I crack in infilled jointed rock masses under impact load, dynamic impact compression tests were implemented by a split Hopkinson pressure bar (SHPB) system and a crack propagation measurement device. The single cleavage triangle (SCT) specimens with the joints filled by gypsum, cement, and marble glue were adopted. The dynamic propagation processes and impact failure modes of the crack were analyzed, and the evolution laws of stress intensity factor and energy release rate during the dynamic propagation of mode I crack were studied by the experimental-numerical method. The results show that there are three main failure modes of the infilled jointed rock masses: the prefabricated crack extends and penetrates the whole specimen, the infilled joint fails after the crack penetration, and the infilled joint fails first and then blocks the crack penetration. The failure of the filling body in the joint is related to the strength and cementation force of the filling body, as well as the strain rate of the dynamic load. The crack propagation speed has an oscillatory growth from the crack initiation point and reaches the maximum at a certain position before the crack penetrates the infilled joint, while the stress intensity factor and energy release rate reach the maximum near the joint. The stiffness degradation of the infilled joint inhibits the crack propagation and causes a sharp increase in the energy release rate. The difference in lithological combinations aggravates the material property mismatch of the rock mass specimens, resulting in different decreases of stress intensity factor and energy release rate as the crack passes through the joint.

Key words: impact load, infilled joint, mode I crack, stress intensity factor, crack propagation speed